Same deal as any virus/spyware. First, if you don't have them, download AVG, Adaware SE, and Spybot Search & Destroy and update them. Then, restart your computer and press F8 while it boots up until it gives you a menu. Start Windows in Safe Mode.
Run all the tools in safe mode and remove everything they find. You have to restart again in safe mode and re-run the tools to get everything. If that doesn't work, find out what files are causing the problem and delete them. If they resist deletion, google ways to delete stubborn files.
Dan